Apparatus for producing hydrate slurry

ABSTRACT

An apparatus produces hydrate slurry, which is a mixture of aqueous solution and hydrate, by cooling aqueous solution containing a guest compound, which generates the hydrate at temperature higher than 0° C., by using a cooling medium. The apparatus includes a first heat exchanger for supercooling the aqueous solution while holding the aqueous solution in a liquid state and in a second heat exchanger, which is provided on the downstream side of the first heat exchanger for cooling hydrate slurry.

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/JP03/03049 filed Mar. 14, 2003.

FIELD OF THE INVENTION

The present invention relates to an apparatus for generating hydrateslurry. The present invention relates, particularly, to an apparatus forgenerating hydrate slurry that is usable for a cold transporting mediumin an air-conditioning facility or an industrial facility to use coldthermal storage.

BACKGROUND OF THE INVENTION

When aqueous solution that contains a guest compound (herein, the guestcompound is formed as salts. That is, such as tetra-n-butyl ammoniumsalt, tetra-iso-amyl ammonium salt, tetra-iso-butyl phosphonium salt,tri-iso-amyl sulfonium salt and etc.). The aqueous solution is cooled,the guest compound is enclosed in a cage-shaped clathrate lattice formedby water molecules, which are host molecules. And the guest compound iscrystallized to form a hydrate (liquid clathrate hydrate). The hydrateis generated at equal or higher temperature of 0° C. at atmosphericpressure. The hydrate makes it possible to store the cold heatingamount, whose value is several times that of cold water because of thebigger latent heat. The hydrate is composed of fine crystal grains. Andthe hydrate is suspended in aqueous solution, so that the hydrate existsin a shape of hydrate slurry, which possesses relatively high fluidity.Therefore, such hydrate slurry possesses a preferable characteristicusable for a cold transporting medium for an air-conditioning facilityor for an industrial facility to use a cold thermal storage.

Conventionally, cooling aqueous solution that contains a guest compoundhas generated the above-described hydrate slurry, by means of exchangingheat between the cold medium (such as cold water) and the aqueoussolution, by using one set of the heat exchanger. In this case, when theaqueous solution that contains a guest compound is cooled, supercoolingoccurs. As a result, the hydrate sometimes exists as a form of theaqueous solution at the lower temperature than the temperature, at whichthe hydrate generates. After the aqueous solution is supercooled in theheat exchanger, supercooling the aqueous solution is canceled on a heattransfer surface in the heat exchanger. At such a procedure, thegenerated hydrate is easy to be adhered to the heat transfer surface inthe heat exchanger. The adhesion degrades the heat transfer performanceof the heat exchanger. Furthermore, some case happens that the aqueoussolution is supercooled to a great extent in the heat exchanger, andafterwards, supercooling is canceled. In such a case, the hydrate isgenerated rapidly, so that the viscosity of the hydrate slurryincreases, and also the flow resistance and the pressure lossesincrease. As a result, the corresponding pump power is required toincrease. And in the worst case, blocking happens in some part of theheat exchanger. As described above, it causes an unstable systemoperation to cancel the supercooling of aqueous solution in the heatexchanger.

Additionally, in order for the conventional method to generate thehydrate slurry that possesses a predetermined heat density, the coldwater cooled by a refrigerating machine and the aqueous solution thatcontains a guest compound are transported in some sorts of the heatexchanger. The heat exchanger has a large heat transfer area, such as aplate type one or a multitubular type one. In the conventional method,the mutual materials are exchanged in such a way.

The reason why the above-mentioned disadvantage happens is that it isdifficult to generate directly the hydrate slurry that has apredetermined heat density by cooling the aqueous solution, whichcontains a guest compound by means of exchanging the mutual heat in anevaporator of the refrigerating machine. That is to say, if an attemptis made to generate the hydrate slurry by means of exchanging the mutualheat in the evaporator, the heat resistance increases. Because theviscosity of the hydrate slurry is higher than that of water and thehydrate is apt to adhere to the cooling surface. On the other hand,since the heat transfer area of evaporator is small, it may be that theheat resistance is large, it is very difficult to generate directly thehydrate slurry that has the predetermined heat density.

However, in the above-described conventional apparatus for generatingthe hydrate slurry, a pump for cold water and a pump for hydrate slurryare required, in addition to a plate type or multitubular type heatexchanger. This requirement invited some sorts of problems such that theequipment cost becomes higher and the energy consumption becomes higher.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for generating hydrateslurry efficiently by preventing aqueous solution on a heat transfersurface in a heat exchanger from canceling the supercooling.

In order to attain the object, the present invention provides anapparatus for generating hydrate slurry. The hydrate slurry is a mixtureof aqueous solution and a hydrate. Cooling aqueous solution thatcontains a guest compound by using a cooling medium generates thehydrate slurry. The guest compound generates the hydrate at temperatureof more than 0° C. The apparatus comprises a first heat exchanger and asecond heat exchanger. The first heat exchanger supercools the aqueoussolution during holding the aqueous solution in a liquid state. And thesecond heat exchanger cools the hydrate slurry. The second heatexchanger is located on the downstream side of the first heat exchanger.

In accordance with the present invention, when generating the hydrateslurry in the apparatus, it is preferable that means for canceling thesupercooling of aqueous solution are located between the first heatexchanger and the second heat exchanger.

In the apparatus for generating the hydrate slurry, in accordance withthe present invention, it is preferable that a plurality of the secondheat exchangers is provided so as to be switchable.

As means for canceling the supercooling, for example, means forinjecting hydrate slurry into supercooled aqueous solution are cited. Inthe present invention, it is preferably equal or higher than 0.7° C.,how degree the aqueous solution is supercooled by the first heatexchanger. Here, the supercooling degree is defined as a differencebetween the starting temperature, at which the hydrate begins togenerate from the aqueous solution possessing a determined concentrationand the temperature of the supercooled aqueous solution. Also, it ispreferable that the quantity of the hydrate slurry injected into theaqueous solution supercooled by the first heat exchanger is 1 vol % ormore, more preferably 1.8 vol % or more, of the total quantity of theaqueous solution. Also, the Reynolds number of the aqueous solution ispreferably 4500 or more.

The hydrate slurry introduced into the supercooled aqueous solution maybe the hydrate slurry generated by the second heat exchanger, or may bethe hydrate slurry stored in a thermal storage tank for the hydrateslurry.

Also, as means for canceling the supercooling, a cooling portion of asmall refrigerating machine, a low-temperature protrusion, anoscillating portion of an ultrasonic oscillator, a low-frequencyoscillator, a static mixer, a mixing blade, a pump, or the like is used.

As described above, when a plural of the second heat exchanger isprovided so as to be switchable, the operation can be switched over, asdescribed below. For example, when adhered hydrate is detected in thesecond heat exchanger to be used to generate the hydrate slurry amongthe plural of the second heat exchanger, it makes it possible to operatethe system in such a way that the hydrate slurry stops being generatedin the second heat exchanger. And in this case, the second heatexchanger is switched over to another one to continue to generate thehydrate slurry. And, the hydrate slurry in the second heat exchanger, inwhich it stopped generating the hydrate slurry, starts melting. Also,the plurality of the second heat exchanger may be switched oversuccessively at the fixed time interval for performing the meltingoperation.

In order to attain another object, the present invention provides anapparatus for generating hydrate slurry. The apparatus enables the costto be reduced, and the apparatus enables the energy to be saved, byeconomizing a plate type or multitubular type heat exchanger and a pump.

In order to attain the above-mentioned objects, the present inventionprovides an apparatus for generating hydrate slurry that containshydrate of guest compound by cooling aqueous solution that contains aguest compound, which generates hydrate at equal or high temperature of0° C.

The apparatus comprises:

-   -   a refrigerating machine having a plurality of evaporators        provided so as to be switchable;    -   a composed circulation system for the aqueous solution of the        guest compound, so as to cool the aqueous solution of the guest        compound by each of said evaporators;    -   control means for stopping cooling the aqueous solution of the        guest compound in one evaporator when the circulation system for        the aqueous solution of the guest compound in the evaporator is        blocked, and for starting cooling the aqueous solution of the        guest compound in another evaporator; and    -   means for supplying a high-temperature refrigerant in said        refrigerating machine to an evaporator, in which cooling the        aqueous solution of the guest compound stops.

In accordance with the present invention, the apparatus for generatinghydrate slurry preferably provides means for detecting whether or notthe circulation system arranged in the evaporator is blocked by hydrate.

As one of the detecting means, at least one of the following is used.For instance, the means are a flow-meter, a thermometer provided on anoutlet pipe from the evaporator of the circulation system and adifferential pressure gage provided across an inlet pipe to theevaporator of the circulation system and the outlet pipe from theevaporator.

As for generating the hydrate slurry in accordance with the presentinvention, for instance, a generating apparatus which has therefrigerating machine as an absorption refrigerating machine. And theapparatus has means for supplying refrigerant gas generated in thegenerator to the evaporator in which cooling the aqueous solution of theguest compound stops.

In accordance with the present invention, the apparatus for generatingthe hydrate slurry may be the refrigerating machine, which is acompression refrigerating machine, and which has means for supplyingrefrigerant gas generated in the compressor to the evaporator, wherecooling aqueous solution of the guest compound stops.

Furthermore, the apparatus for generating the hydrate slurry, may be acase, the refrigerating machine, which is the compression refrigeratingmachine, and which has means for supplying refrigerant liquid generatedin a condenser to the evaporator, where cooling aqueous solution of theguest compound stops.

In accordance with the present invention, the apparatus for generatingthe hydrate slurry is preferable, in which the aqueous solution of theguest compound is supercooled in the circulation system arranged in theevaporator. And the apparatus has means for canceling the supercooledstate of the supercooled aqueous solution to generate the hydrateslurry. The means are located on an outlet pipe of the circulationsystem for the aqueous solution of the guest compound from theevaporator.

As the means for canceling supercooling, a cooling portion of a smallrefrigerating machine, a low-temperature protrusion, an oscillatingportion of an ultrasonic oscillator, a low-frequency oscillator, hydrateslurry injecting means, a static mixer, a mixing blade, a pump, or thelike can be applied to the apparatus.

As the guest compound used in the apparatus generating the hydrateslurry, at least one kind selected from a group consisting oftetra-n-butyl ammonium salt, tetra-iso-amyl ammonium salt,tetra-iso-butyl phosphonium salt, and tri-iso-amyl sulfonium salt isused.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of an air-conditioning system including anapparatus for generating hydrate slurry, as one example of the presentinvention.

FIG. 2 is a chart showing the presence and absence of canceling thesupercooling under conditions of the injection rate of hydrate slurryand the degree of supercooling of aqueous solution, as one example ofthe present invention;

FIG. 3 is a chart showing the presence and absence of canceling thesupercooling under conditions of the Re number of aqueous solution andthe injection rate of hydrate slurry, as one example of the presentinvention;

FIG. 4 is a schematic drawing of an apparatus for generating hydrateslurry, which has a small type heat exchanger for injecting hydrateslurry, as another example of the present invention;

FIG. 5 is a schematic drawing of an apparatus for generating hydrateslurry, provided with means for canceling the supercooling, as anotherexample of the present invention;

FIG. 6 is a schematic drawing showing one example of means for cancelingthe supercooling, in accordance with the present invention;

FIG. 7 is a schematic drawing showing another example of means forcanceling the supercooling, in accordance with the present invention;

FIG. 8 is a schematic drawing showing another example of means forcanceling the supercooling, in accordance with the present invention;

FIG. 9 is a schematic drawing showing another example of means forcanceling the supercooling, in accordance with the present invention;

FIG. 10 is a schematic drawing showing another example of means forcanceling the supercooling, in accordance with the present invention;

FIG. 11 is a schematic drawing showing one example of an apparatus forgenerating hydrate slurry, in accordance with the present invention;

FIG. 12 is a schematic drawing showing means for detecting blocking andmeans for preventing the apparatus from blocking;

FIG. 13 is a schematic drawing showing one example of means forcanceling the supercooling;

FIG. 14 is a schematic drawing showing another example of means forcanceling the supercooling;

FIG. 15 is a schematic drawing showing another example of an apparatusfor generating hydrate slurry, in accordance with the present invention;and

FIG. 16 is a schematic drawing showing another example of an apparatusfor generating hydrate slurry, in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

The term “guest compound” used in the present invention is defined as acompound, which is enclosed in a cage-shaped clathrate lattice formed bywater molecules, which are host molecules, at temperature of 0° C. ormore. The guest compound is crystallized to generate a hydrate (liquidclathrate hydrate) by cooling the aqueous solution at atmosphericpressure. As the guest compound, tetra-n-butyl ammonium salt,tetra-iso-amyl ammonium salt, tetra-n-butyl phosphonium salt,tetra-iso-amyl sulfonium salt, and the like are cited. The hydrateslurry, where the hydrate of the guest compound is mixed in aqueoussolution, possesses preferable characteristics as a cold transportingmedium for an air-conditioning facility or an industrial facility to usea cold thermal storage. However, as described above, it happens somesort of the problem that the heat transfer performance of the heatexchanger decrease, the pump power increases, resulting in the blockingof heat exchanger, due to canceling the supercooling of aqueoussolution.

In the apparatus for generating the hydrate slurry, a heat exchanger forgenerating the hydrate slurry is separated into the first heat exchangerand the second heat exchanger. The first one is for supercooling aqueoussolution during holding the aqueous solution in a liquid state. Theother one is located downstream to the first heat exchanger in order tocool the hydrate slurry. Therefore, it becomes easy to avoid cancelingthe supercooling in the heat exchanger. As a result, it becomes easy totake the countermeasures against such a problem that is caused bycanceling the supercooling of the hydrate slurry.

Canceling the supercooling of the hydrate slurry prevents the hydrateslurry from being generated rapidly in the heat exchanger. Consequently,the hydrate does not adhere to a heat transfer surface of the heatexchanger. Therefore, it enables the heat exchanger to possess theminimized heat transfer area. And it enables the heat exchanger toincrease the flow velocity of the hydrate slurry without decreasing theflow velocity of the hydrate slurry in the viewpoint of performance. Andthe apparatus for generating the hydrate slurry can obtain the optimizedapparatus for continuing the operation.

Aqueous solution is supercooled heavily in the heat exchanger.Afterwards, the supercooling is canceled. In this case, a hydrate isgenerated suddenly. As a result, the viscosity of the hydrate slurryincreases, resulting in increasing the flow resistance and the pressurelosses. Consequently, the required pump power increases. In the worstcase, the blocking happens in the heat exchanger. As described above,canceling the supercooling of aqueous solution invites the unstablesystem operation in the heat exchanger. The apparatus for generating thehydrate slurry in accordance with the present invention can avoid theaforementioned problems.

In the exemplary embodiment, hereinafter, the first heat exchanger isdefined as a sensible-heat heat exchanger because of absorbing sensibleheat from aqueous solution and because of supercooling the aqueoussolution during keeping the aqueous solution in a liquid state. Thesecond heat exchanger is also defined as a latent-heat heat exchanger.Because the heat exchanger absorbs the latent heat for transferring fromthe aqueous solution to the hydrate (in the actual situation, the heatexchanger absorbs the sensible heat from the hydrate slurry at the sametime), in order to cool hydrate slurry.

The apparatus for generating the hydrate slurry in accordance with thepresent invention, sometimes, provides means for canceling thesupercooling of aqueous solution, which is located between the firstheat exchanger (sensible-heat heat exchanger) and the second heatexchanger (latent-heat heat exchanger). There is hardly fear such ascanceling the supercooling of the aqueous solution in the heatexchanger. So, particularly, canceling the supercooling prevents theheat exchanger from blocking in the heat exchanger.

It may be a case, such as provided means for injecting the hydrateslurry into the supercooled aqueous solution. Such means are those forcanceling the supercooling. In this case, the supercooled degree of theaqueous solution by the first heat exchanger (sensible-heat heatexchanger) is determined to the supercooled degree of equal or higherthan 0.7° C. Otherwise, the quantity of the hydrate slurry injected intothe supercooled aqueous solution by the first heat exchanger isdetermined to the degree of the equal or more than 1 vol %. Preferablythe degree is the equal or more than 1.8 vol %. Regardless of thesupercooled degree, the Reynolds number of the aqueous solution isapplied to canceling the supercooled aqueous solution, whose number isthe equal or more than 4500.

The hydrate slurry injected into the supercooled aqueous solutionobtains the same effect as those resulting from generating the hydrateslurry by the second heat exchanger (latent-heat heat exchanger) orthose resulting from using the hydrate slurry that is stored in athermal storage tank for the hydrate slurry.

Furthermore, the following means obtains the same as the above-mentionedeffect. For instance, a cooling portion of a small refrigeratingmachine, a low-temperature protrusion, an oscillating portion of anultrasonic oscillator, a low-frequency oscillator, a static mixer, amixing blade, a pump, or the like is applied to the means for cancelingthe supercooling of the aqueous solution.

There may be a case that a plurality of the second heat exchanger(latent-heat heat exchanger) is provided so as to be switchable. In sucha case, when the adhered hydrate is detected in the second exchanger,which is used for generating the hydrate slurry, another second heatexchanger is switched over in order to continue generating the hydrateslurry. At the same time, the previous second heat exchanger, whichstopped generating the hydrate slurry, becomes usable formelting-operation. As a result, the hydrate slurry is obtained with highefficiency.

A sign is detected by the method described below, whether the hydrate isadhered to or not and whether the blocking happens or not. For example,there is a sign that the flow resistance is the equal or less than thepredetermined value, or that the flow rate is the equal or less than thepredetermined value. Otherwise, there is a sign that the exchangedheating value is the equal or less than the predetermined value. Suchsigns are detected by measuring the pressure losses, the flow rate, andthe temperature in the pipe.

Furthermore, the melting operation by successive switching over theplurality of the second heat exchanger (latent-heat heat exchanger) atthe fixed time interval makes it possible to eliminate a device fordetecting the adhered hydrate in the second heat exchanger, resulting insimplifying the system.

EXAMPLE

As one of the exemplary embodiments, one example is described inaccordance with the drawing, as follows.

As one example of the present invention, FIG. 1 shows anair-conditioning system that incorporates an apparatus for generatinghydrate slurry. First, essential components in the air-conditioningsystem are schematically explained. A refrigerating machine 1, whichincludes a cooling tower, pump, heat exchangers, etc., generates coldwater serving as a cold thermal medium for cooling aqueous solution andhydrate slurry.

As the heat exchanger for generating the hydrate slurry, a two-stageheat exchanger is provided. A sensible-heat heat exchanger (first heatexchanger) 2 cools the aqueous solution by means for exchanging heatwith the cold water. Two latent-heat heat exchangers (second heatexchangers) 3 a and 3 b located on the downstream side of thesensible-heat heat exchanger 2 cool hydrate slurry by means forexchanging heat with the cold water. Although the cold water generatedby the refrigerating machine 1 is supplied to the sensible-heat heatexchanger 2 and the latent-heat heat exchangers 3 a and 3 b in parallelin the example shown in FIG. 1, the cold water may be supplied to eachdevice in series. The number of latent-heat heat exchangers may be threeor more. The aqueous solution that contains a guest compound is sent tothe sensible-heat heat exchanger 2 from a thermal storage tank 4. Theaqueous solution is cooled to the degree of a supercooled state. Andeither one of the latent-heat heat exchangers 3 a and 3 b further coolsthe hydrate slurry generated by canceling the supercooling of theaqueous solution on the downstream side of the sensible-heat heatexchanger 2. And the hydrate slurry returns to the thermal storage tank4. In the system, an injection pipe is connected to a pipe between thesensible-heat heat exchanger 2 and the latent-heat heat exchangers 3 aand 3 b from a pipe on the downstream side of the latent-heat heatexchangers 3 a and 3 b. By way of the connected injection pipe, some ofthe hydrate slurry is injected into the aqueous solution in asupercooled state. Such process brings up canceling the supercooling ofthe aqueous solution. The hydrate slurry is sent from the thermalstorage tank 4 to air-conditioner load 6, and the aqueous solution,whose cold thermal storage is consumed in the air-conditioner load 6,returns to the thermal storage tank 4. From a hot water tank 7, hotwater is sent to the latent-heat heat exchanger 3 a or 3 b that requiresmelting operation for the hydrate slurry.

Although the aqueous solution and the hydrate slurry are cooled by usingthe cold water generated by the refrigerating machine 1 as a coolingmedium in FIG. 1, the cold water taken out of, for example, an icethermal storage tank may be usable for a cooling medium. Also, althoughthe thermal storage tank 4 is provided in FIG. 1, the thermal storagetank is not always required. And the hydrate slurry generated by thelatent-heat heat exchanger may be sent directly to the air-conditionerload.

Herein after, the operation of the air-conditioning system shown in FIG.1 is explained in more detail.

When the system starts, there is no hydrate slurry. And the aqueoussolution that contains a guest compound (for example, tetra-n-butylammonium bromide (TBAB)) is stored in the thermal storage tank 4. Theconcentration of the guest compound in the aqueous solution isdetermined, which is suitable to the air-conditioner load in theair-conditioning system. Changing the concentration enables the heatdensity of the hydrate slurry and the temperature of cold water to bevariable, so as to be suitable to the air-conditioner load, provided inthe air-conditioning system. In the exemplary example, the concentrationis determined to be about 20-wt %. Before it starts operating theair-conditioning, the hydrate slurry has been prepared. First, theaqueous solution in the thermal storage tank 4 is circulated to thethermal storage tank 4 through the sensible-heat heat exchanger 2 andone latent-heat heat exchanger 3 a by using a generation pump 12. Theother latent-heat heat exchanger 3 b is not used. Next, therefrigerating machine 1 is operated to circulate cold water of 4 to 6°C. generated by the heat exchanger in the refrigerating machine 1 to theheat exchanger in the refrigerating machine 1 through the sensible-heatheat exchanger 2 and the latent-heat heat exchanger 3 a by using a coldwater pump 11. At the same time, the aqueous solution is cooled by thesensible-heat heat exchanger 2 to the degree such that supercooling iscanceled naturally, and a small quantity of the hydrate slurry isgenerated. Further, the hydrate slurry is generated to the extent ofenabling the system to operate for the load of the air-conditioning,while the hydrate slurry is cooled by the latent-heat heat exchanger 3a. Thus, first, the aqueous solution is flown in the apparatus forgenerating the hydrate slurry. And afterwards, the cooling water as acooling medium is flown. Such a process prevents the latent-heat heatexchanger from blocking, during generating the hydrate slurry.

Next, the aqueous solution is supercooled by the sensible-heat heatexchanger 2. The degree of supercooling the aqueous solution isdetermined to set at 0.7° C. or more (the temperature of the aqueoussolution will not be equal or lower than the temperature of the coldwater, which is a cooling medium). Then, an injection pump 13 operatesin order to inject the hydrate slurry into the aqueous solution in asupercooled state. Here, the aqueous solution in a supercooled stateflows in the pipe between the sensible-heat heat exchanger 2 and thelatent-heat heat exchanger 3 a. And here, the hydrate slurry is injectedfrom the pipe on the downstream side of the latent-heat heat exchanger 3a by way of the injection pipe 5. The hydrate in the injected hydrateslurry serves as a nucleus for generating the hydrate in the aqueoussolution. Thus, the supercooled state of the aqueous solution, which issupercooled by the sensible-heat heat exchanger 2, is canceled togenerate the hydrate slurry, which has a low solid phase ratio.Subsequently, the hydrate slurry is further cooled by the latent-heatheat exchanger 3 a. Since the hydrate slurry is sent to the latent-heatheat exchanger 3 a, supercooling has already been canceled at that time.At such a time, the flow rate of the cold water is controlled, whichflows into the latent-heat heat exchanger 3 a. The hydrate slurry, whichpossesses a desired heat density according to the load forair-conditioner 6, is generated. Thus, the operation can be shifted to ahighly efficient operation to generate the hydrate slurry. And theair-conditioning can initialize the operation.

At the time of the air-conditioning operation, the aqueous solution of10 to 12° C., which has returned to the thermal storage tank 4 from theload for air-conditioner 6, is sent to the sensible-heat heat exchanger2 by the generation pump 12 and is supercooled to degree of thetemperature 5 to 7° C. Supercooling is canceled by injecting the hydrateslurry through the injection pipe 5, which leads to generating thehydrate slurry, whose degree is about 7.4° C. The hydrate slurry isfurther cooled by the latent-heat heat exchanger 3 a and the hydrateslurry returns to the thermal storage tank 4. From the thermal storagetank 4, the hydrate slurry possessing the degree of about 6.5° C. issent to the load for air-conditioner 6, by a load pump 14. At this time,the heat density of hydrate slurry is controlled so that the total powerto be required for both conveying power to the heat exchanger andconveying power to the load is minimized. In the way, it becomespossible to save the energy to operate the apparatus.

During operating the air-conditioning system, judging from the viewpointthat the hydrate slurry begins to adhere to the heat transfer surface ofthe latent-heat heat exchanger 3 a, generating the hydrate slurry in thelatent-heat heat exchanger 3 a stops, in order to prevent the hydrateslurry form blocking. And the hydrate slurry continues to generate,switching over the heat exchanger to the latent-heat heat exchanger 3 b.The latent-heat heat exchanger 3 a enters into the operation stage formelting. It is judged whether the hydrate slurry adheres to the heattransfer surface of the latent-heat heat exchanger or not, by monitoringthe flow rate of the hydrate slurry with a provided flowmeter (not shownin the drawing). For example, such judgment is done, based on monitoringthe flow rate of the hydrate slurry. And the judgement is done, based ondetecting that the introduced flow rate of the hydrate slurry into thelatent-heat heat exchanger reduces. Similarly, it is also judged whetheror not the hydrate slurry adheres to the heat transfer surface of thelatent-heat heat exchanger. The judgement is based on the increasedamount of the pressure losses, and based on the decreased amount that isthe temperature difference between the inlet and the outlet of the coldwater or the hydrate slurry, which is supplied to the latent-heat heatexchanger.

Hereinafter, it is explained how to operate the melting operation.Supplying the cold water to one latent-heat heat exchanger 3 a stops. Onthe contrary, and supplying the cold water to the other latent-heat heatexchanger 3 b starts. By switching over the usable heat exchanger fromthe latent-heat heat exchanger 3 a to the latent-heat heat exchanger 3 bin this manner, hydrate slurry continued to be generated continuously.To the latent-heat heat exchanger 3 a, which is not supplied with thecold water, the hot water is supplied from a hot water tank 7 in orderto melt the adhered hydrate slurry to the heat transfer surface in theheat exchanger. Although the hot water for melting, which is warmed by aheater in the hot water tank 7, is used in FIG. 1, water on thedownstream side of the latent-heat heat exchanger may be usable for themelting operation.

In the above mentioned description, in case that the flow rate of thehydrate slurry to the latent-heat heat exchanger decreases, in case thatthe exchanged heating value decreases, or in case that the pressurelosses increases, the melting operation is done. Contrarily, if themelting operation is performed by successively switching over aplurality of latent-heat heat exchangers at the fixed time interval,detection instruments such as a flowmeter pressure gage, and thermometeris eliminated. The elimination enables the system to be simplified.

As mentioned above, the heat exchanger for generating the hydrate slurryis separated into the two sorts of the heat exchanger. One is asensible-heat heat exchanger for supercooling aqueous solution in aliquid state. And the other is a latent-heat heat exchanger for coolinghydrate slurry. And providing a plurality of switchable latent-heat heatexchangers surely makes it possible to prevent the latent-heat heatexchanger from blocking in the device. And then, hydrate slurry can begenerated continuously with high efficiency.

Next, in the exemplary embodiment, the result is obtained by studyingthe proper conditions for the degree of supercooling the aqueoussolution by the sensible-heat heat exchanger 2. Furthermore, the resultis obtained, which is the injection rate of the hydrate slurry injectedinto the aqueous solution in order to cancel the supercooling of theaqueous solution.

In FIG. 2, the abscissa represents the injection rate of the hydrateslurry (volume ratio of the hydrate slurry to the total quantity of theaqueous solution). The ordinate represents the degree of supercoolingthe aqueous solution for various concentrations of the guest compound inthe aqueous solution. The conditions, in which supercooling wascanceled, is indicated by ◯. And the conditions, in which supercoolingwas not canceled, is indicated by X. Whether or not canceling thesupercooling is present (absent or not) is judged from the viewpoint ofwhether or not a rising temperature is detected due to canceling thesupercooling by using the thermometers provided on the upstream anddownstream sides of the injection portion of the hydrate slurry.

As seen from FIG. 2, if the degree of supercooling the aqueous solutionis equal or higher than 0.7° C. or if the injection rate of the hydrateslurry is the equal or higher than 1 vol % of the flow rate of theaqueous solution, it is almost enough to cancel the supercooling of theaqueous solution. Furthermore, if the injection rate of the hydrateslurry is the equal or higher than 1.8 vol % of the flow rate of theaqueous solution, supercooling the aqueous solution is, surely,canceled. Thus, a small quantity of the injected hydrate slurry sufficesfor canceling the supercooling of the aqueous solution. And most of theremaining hydrate slurry is used for the load for air conditioner 6.

And, furthermore, the result resulting from studying is described below,that is, the conditions in which supercooling the aqueous solution iscanceled regarding the Reynolds (Re) number of the aqueous solution. TheRe number is determined to be Re=D·U·ρ/η, using pipe diameter (D), flowvelocity of aqueous solution (U), density (ρ), and coefficient ofviscosity (η). In FIG. 3, the abscissa represents Re number, and theordinate represents injection rate of the hydrate slurry. The conditionin which supercooling was canceled is indicated by ◯, and the conditionin which supercooling was not canceled is indicated by X. Thisexperiment was conducted at the degree of supercooling the aqueoussolution about 0.8° C. and at the injection rate of the hydrate slurrythat is the equal or higher than 2 vol %.

Looking at FIG. 3, it is found that when the Reynolds number of theaqueous solution is the equal or larger than 4500, the hydrate slurry isinjected into the system and supercooling the aqueous solution is,surely, canceled. As a result, the hydrate slurry can be generatedefficiently and stably.

Next, an apparatus for generating hydrate slurry in accordance withanother example of the present invention is described below.

In FIG. 1, the injection pipe 5 is connected to the pipe between thesensible-heat heat exchanger 2 and the latent-heat heat exchangers 3 aand 3 b from the pipe on the downstream side of the latent-heat heatexchangers 3 a and 3 b. From such injection pipe, the part of thehydrate slurry generated by the latent-heat heat exchanger is injectedinto the aqueous solution in a supercooled state. Instead, as shown inFIG. 4, a small size of the heat exchanger for generating the hydrateslurry 20 may be provided separately to beforehand prepare the hydrateslurry to be injected. FIG. 4 shows a portion of the apparatus forgenerating the hydrate slurry, which includes the sensible-heat heatexchanger 2, the latent-heat heat exchangers 3 a and 3 b, the thermalstorage tank 4, the heat exchanger for generating the hydrate slurry 20provided on the injection pipe 5, and pipes for connecting theseelements each other. As the heat exchanger for generating the hydrateslurry 20, a small size plate type heat exchanger, an enclosed tankjacket type heat exchanger, or the like are used. If the hydrate slurrygenerating heat exchanger 20 is provided in this manner, the system canstart quickly. Also, a buffer tank may be added to the hydrate slurrygenerating heat exchanger 20, according to the necessity, to beforehandprepare the hydrate slurry that is required at the starting time.Furthermore, in the air-conditioning system provided with the thermalstorage tank 4 as shown in FIG. 1, the hydrate slurry in the thermalstorage tank 4 may be used.

As mentioned above, the apparatus for generating the hydrate slurry isused for injecting the hydrate slurry on the downstream side of thesensible-heat heat exchanger 2 to cancel the supercooling of the aqueoussolution. Instead, as shown in FIG. 5, means for canceling supercooling30 may be provided in the pipe between the sensible-heat heat exchanger2 and the latent-heat heat exchangers 3 a and 3 b. FIG. 5 shows only aportion of the hydrate slurry generating apparatus including thesensible-heat heat exchanger 2, the latent-heat heat exchangers 3 a and3 b, the thermal storage tank 4, pipes for connecting these elementseach other, and the means for canceling supercooling 30.

Examples of the means for canceling supercooling 30 are shown withreference to FIGS. 6 to 10.

The means for canceling supercooling shown in FIG. 6 consists of acooling portion 32 connected to a small refrigerating machine 31, andthe cooling portion 32 is inserted in a pipe 21 from the outside. Asshown in FIG. 6, the cooling portion 32 provided in the pipe 21 iscooled to degree of the equal or lower than the temperature forgenerating the hydrate by the small refrigerating machine 31, and thusthe hydrate adheres to the surface. When the aqueous solution, which hasbeen supercooled by the sensible-heat heat exchanger 2, gets in contactwith the cooling portion 32, the hydrate adhering to the surface of thecooling portion 32 activates as a product nucleus.

Therefore, supercooling is canceled and then, it becomes easy togenerate the hydrate.

As the means for canceling supercooling, a low-temperature protrusionhaving a Peltier element may be inserted in the pipe 21. Such alow-temperature protrusion is, like the cooling portion of the smallrefrigerating machine shown in FIG. 6, also cooled to degree of thetemperature, which is the equal or lower than the temperature ofgenerating the hydrate in advance, and thus a hydrate is kept to beadhered to the surface. When the aqueous solution having beensupercooled gets in contact with the low-temperature protrusion, thehydrate adhering to the surface of the low-temperature protrusion actsas a product nucleus, so that supercooling is canceled and it becomeseasy to generate the hydrate.

The means for canceling supercooling shown in FIG. 7 have a oscillatingportion 34 connected to an ultrasonic oscillator 33, and the oscillatingportion 34 is inserted in the pipe 21 from the outside. When the aqueoussolution having been supercooled by the sensible-heat heat exchanger 2gets in contact with the oscillating portion 34, supercooling iscanceled by the oscillation, and thus it becomes easy to generate ahydrate.

Also, instead of ultrasonic waves, oscillation with a low frequency ofseveral hertz to several hundred hertz may be used.

The means for canceling supercooling shown in FIG. 8 have a static mixer38 having a mechanism such as a twisted plate for reversing and mixing afluid, which is provided in the pipe 21. The static mixer 38 stirs thesupercooled aqueous solution, so that the supercooling is canceled andit becomes easy to generate a hydrate.

The means for canceling supercooling shown in FIG. 9 have a mixing bladewhich is housed in a vessel inserted in an intermediate portion of thepipe 21 and is rotated by a motor 39. The mixing blade 40 stirs thesupercooled aqueous solution, so that supercooling is canceled and itbecomes easy to generate a hydrate.

The means for canceling supercooling shown in FIG. 10 have a pump 50, inwhich an impeller is rotated in a pump casing provided in anintermediate portion of the pipe 21. The pump 50 stirs the supercooledaqueous solution, so that supercooling is canceled and it becomes easyto generate a hydrate.

The configuration may be such that a bypass pipe is provided on the pipe21 between the sensible-heat heat exchanger 2 and the latent-heat heatexchangers 3 a and 3 b. And the means for canceling supercooling asshown in FIGS. 6 to 10 is provided in this bypass pipe. Also, the numberof means for canceling supercooling is not limited to one, and the meansfor canceling supercooling may be provided at a plurality of location.Further, a plurality of means for canceling supercooling a differenttype may be combined to be used.

As described above, according to the present invention, a system isprovided for generating the hydrate slurry efficiently. In the heatexchanger of the system, supercooling is cancelled, and then, suchcanceling prevents the hydrate from generating rapidly. Therefore, itbrings up no adhered hydrate to the heat transfer surface in the heatexchanger.

Consequently, the exemplary embodiment makes it possible to minimize theheat transfer area of the heat exchanger. And the exemplary embodimentmakes it possible to increase the flow velocity of the hydrate slurry,without decreasing the performance of the heat transfer. As a result,the exemplary embodiment invites the apparatus for generating thehydrate slurry and the method for generating the hydrate slurry in theoptimized way.

Embodiment 2

In the exemplary embodiment of the apparatus for generating the hydrateslurry in accordance with the present invention, a circulation systemfor the aqueous solution of the guest compound is located in anevaporator of a refrigerating machine, in order to cool the aqueoussolution of the guest compound. In the exemplary embodiment, a heatexchanger for generating the hydrate slurry is not required, comparedwith in a conventional system. So, the exemplary embodiment enables thesystem to be simplified. Furthermore, a plurality of evaporators isprovided so as to be switchable. And when blocking begins in the processof circulating the aqueous solution of the guest compound in oneevaporator, it stops cooling the aqueous solution of the guest compoundin the evaporator. On the contrary, another evaporator starts coolingthe aqueous solution of the guest compound. In such a way, since thecirculation system for the aqueous solution of the guest compound, whichhas entered into the blocking stage, is not used. Therefore, it is notrequired to increase the pump power for transporting the aqueoussolution of the guest compound.

Furthermore, a high-temperature refrigerant in the refrigerating machineis supplied to the evaporator. At that time, in the evaporator, it hasalready stopped cooling the aqueous solution of the guest compound. Inthe circulating process, the operation for melting the hydrate, whichhas entered into the blocking stage, is done by utilizing the heatinside the refrigerating machine. As a result, it becomes obtainable tosave the energy.

Furthermore, in the apparatus for generating the hydrate slurry inaccordance with the exemplary embodiment, the means for detecting thatthe circulation system located in the evaporator have entered into theblocking stage. The above-mentioned means make it possible to stopgenerating the hydrate slurry in one evaporator. On the contrary, themeans make it possible to start generating the hydrate slurry in anotherevaporator. In this case, the mutual evaporators are switched overautomatically and quickly.

Further, in the apparatus for generating the hydrate slurry inaccordance with the exemplary embodiment, the aqueous solution of theguest compound is supercooled in the circulation system located in theevaporator. And means for canceling the supercooled state of the aqueoussolution and for generating the hydrate slurry is provided in the outletpipe of the circulation system for the aqueous solution of the guestcompound from the evaporator. The means enable the hydrate slurry in thecirculation system located in the evaporator to generate. The generatedamount is to the least extent.

The exemplary embodiment can prevent the hydrate form blocking in thecirculation system, and the pump power from increasing.

EXAMPLE

The following is one description of one example of the exemplaryembodiment.

FIG. 11 shows one example of the apparatus for generating the hydrateslurry, in accordance with the exemplary embodiment. The apparatus forgenerating the hydrate slurry uses a double effect an absorptionrefrigerating machine 110, which has a double effects, and which useswater as a refrigerant and lithium bromide (LiBr) as an absorbent. Theessential components of such a absorption refrigerating machine are twoevaporators 120 a and 120 b, which are also used as a heat exchangersfor generating hydrate slurry, an absorber 130, a first generator 140, asecond generator 150, and a condenser 160. Furthermore, a cooling tower170 is provided for supplying cooling water, which is used in thecondenser 160 and the like.

Aqueous solution of the guest compound in a thermal storage tank 101 istransported into a heating tube located in the evaporator by an aqueoussolution pump 102. And the aqueous solution is supercooled. That is tosay, the aqueous solution possesses the lower temperature than thegenerating temperature of the hydrate, but the aqueous solution remainsin a liquid state. As described later, the aqueous solution, which hasbeen supercooled in the evaporator, are canceled to be supercooled bymeans for canceling supercooling (not shown in FIG. 11). And then, theaqueous solution becomes hydrate slurry, and returns back to the thermalstorage tank 101. At this time, a first hydrate and a second hydratewith a different hydration number respectively (the temperaturegenerating the second hydrate is higher than that of the first hydrate)exist, may be in a case, the existence is influenced by theconcentration the aqueous solution of the guest compound. In such aconcentration area, canceling the supercooling generates the secondhydrate. As described later, there is a circulation system for theaqueous solution of the guest compound. In such a circulation system,the aqueous solution returns back to the thermal storage tank 101through the heating tube located in the evaporator from the thermalstorage tank 101. Means for detecting whether or not the inside of theheating tube has entered into the blocking stage by the adhered hydrateslurry is provided in the stage. (not shown in FIG. 1). The hydrateslurry in the thermal storage tank 101 is transported into a load 105 byusing a slurry pump 104. In the load 105, the cold heat of the hydrateslurry is utilized, and the hydrate slurry turns to the aqueous solutionand returns back to the thermal storage tank 101.

In the exemplary embodiment, there is one case where an operation forgenerating the hydrate slurry is done, using the evaporator 120 a.

The aqueous solution of the guest compound in the thermal storage tank101 flows in a heating tube 103 a located in the evaporator 120 a, byusing the aqueous solution pump 102. The water, which is condensed bythe condenser 160, is transported into the evaporator 120 a through apipe 162 by using a pump 161 a. And the water is sprayed onto theevaporator 120 a and the water evaporates on the surface of the heatingtube 103 a. As a result, the aqueous solution of the guest compound,which flows into the heating tube 103 a, is cooled. Steam, which isevaporated in the evaporator 120 a, is sent into the absorber 130through a pipe 121 a.

In the absorber 130, solution, which has the concentrated value of LiBrand which is supplied from the second generator 150, is sprayed out froma nozzle 131. In the absorber 130, a cooling water pipe 172 is located,which runs from the cooling tower 170 through the condenser 160. Coolingwater in the cooling tower 170 is transported into the cooling waterpipe 172, by using a cooling water pump 171. Solution, which has theconcentrated value of LiBr and which is sprayed into the absorber 130,is cooled by the cooling water that flows in the cooling water pipe 172.And the absorbing performance of the steam (vaporized water) is promotedto be a high degree. The vaporized water from the evaporator 120 a isabsorbed by solution, which has the concentrated value of LiBr. Thesolution concentrating LiBr and the solution diluting LiBr gather at thebottom of the absorber 130. The solution diluting LiBr at the bottom ofthe absorber 130 is transported into the first generator 140 through apipe 133 by using an absorbed solution pump 132.

A heating tube 141 is provided in the first generator 140. And lowtemperature steam is fed into the heating tube 141. The low temperaturesteam is generated by a heat source possessing relatively lowtemperature, such as exhaust heat from the factory. The low-temperaturesteam, which is supplied to the heating tube 141, heats the solutiondiluting LiBr, which is fed from the absorber 130. And, the water isevaporated to dilute the solution concentrating LiBr. The solutiondiluting LiBr is fed into the second generator 150 through a pipe 142.Furthermore, the vaporized water generated in the first generator 140passes through the solution concentrating LiBr in the second generator150 through a pipe 143. And the vaporized water is further fed into thecondenser 160 through a pipe 144.

In the solution concentrating LiBr in the second generator 150, the pipe143 is located. The vaporized water generated in the first generator 140flows in the pipe. The vaporized water enables the solutionconcentrating LiBr, which flows in the pipe 143, to be heat. And wateris evaporated, resulting in further concentrating the concentratedsolution of LiBr. The concentrated solution of LiBr, which has beenconcentrated at the two separate stages in the above-mentioned manner,restore the absorbing performance of the vaporized water. And then, thesolution is supplied to the nozzle 131 in the absorber 130, and is usedfor absorbing the vaporized water from the evaporator 120 a.Furthermore, the vaporized water generated in the second generator 150is fed into the condenser 160 through a pipe 152.

The cooling water pipe 172 is located in the condenser 160, so that thecooling water from the cooling tower 170 may flow. The cooling water,which flows in the cooling water pipe 172, enables the vaporized watergenerated in the first generator 140 and in the second generator 150 tocondense. The condensed water in the condenser 160 is fed to thegenerator 120 a.

Such a refrigerating cycle makes it possible to supercool the aqueoussolution of the guest compound, which has possessed about 12° C. andwhich has been supplied from the thermal storage tank 101. And then,supercooling is canceled outside the evaporator 120 a, resulting ingenerating the hydrate slurry. The generated hydrate slurry of about 5°C. in this manner returns back to the thermal storage tank 101. Themeans for canceling supercooling will be described later.

However, when the above-described hydrate slurry is generated in theoperation, the hydrate adheres to the inside of the heating tube 103 alocated in the evaporator 120 a, and blocking sometimes begins in theheating tube 103 a.

When a sign, which means whether or not blocking happens, is detected inthe heating tube 103 a located in the evaporator 120 a, the operationgenerating the hydrate slurry in the evaporator 120 a stops. Afterwards,one evaporator is switched over to another evaporator 120 b to continuethe operation generating the hydrate slurry.

In the exemplary embodiment, solenoid-operated valves 163 a and 122 aare closed. It stops transporting the condensed water from the condenser160 to the evaporator 120 a, and it stops transporting the vaporizedwater from the evaporator 120 a to the absorber 130. And then,solenoid-operated valves 163 b and 122 b open. Transporting starts,which is the condensed water from the condenser 160 to the evaporator120 b. Thus, the operation generating the hydrate slurry continues byusing the evaporator 120 b.

On the other hand, the evaporator 120 a enters into the stage of themelting operation, in which the operation generating the hydrate slurryhas stopped. For the melting operation, either the steam generated inthe second generator 150 or the condensed water at the outlet of thesecond generator 150 is used for a heat source for melting.

Hereinafter, one case is described that using the steam generated in thesecond generator 150 as a heat source for melting performs the meltingoperation. In such a case, a bypass pipe 153 provided with asolenoid-operated valve is attached to the steam pipe 152. The steampipe is located between the second generator 150 and the condenser 160.Here, some of the vaporized water generated in the second generator 150is transported to the evaporator 120 a in order to melt the adheredhydrate to the inside of the heating tube 103 a. That is to say,detecting a blocking sign in the heating tube 103 a, thesolenoid-operated valves 163 a and 122 a are closed, as described above.Keeping on such state, a solenoid-operated valve 154 a in the bypasspipe 153 opens, in order to transport part of the vaporized watergenerated in the second generator 150 into the evaporator 120 a.

It may be a case that the melting operation is performed, using thecondensed water at the outlet of the second generator 150 as a heatsource for melting. In such a case, a bypass pipe 145 provided with asolenoid-operated valve is attached to the pipe 144 for condensed waterbetween the second generator 150 and the condenser 160. In such a way,part of the condensed water at the outlet of the second generator 150 istransported to the evaporator 120 a in order to melt the adhered hydrateinto the inside of the heating tube 103 a. That is to say, detecting ablocking sign in the heating tube 103 a, the solenoid-operated valves163 a and 122 a are closed as described above. Keeping on such state, asolenoid-operated valve 146 a in the bypass pipe 145 opens fortransporting part of condensed water at the outlet of the secondgenerator 150 into the evaporator 120 a. The above-described meltingoperation enables the evaporator 120 a to be ready and usable for theoperation generating the hydrate slurry again.

Not only in the above-mentioned case but in case that a blocking sign isdetected in the heating tube 103 b located in the evaporator 120 b, theoperation, which generates the hydrate slurry in the evaporator 120 b,stops. And switching over the evaporator to the evaporator 120 a, theoperation generating the hydrate slurry continues.

Furthermore, the means for detecting blocking in the heating tubelocated in the evaporator and means for preventing detecting areexplained with reference to FIG. 12. In FIG. 12, the evaporator 120 a isdescribed merely. But, the evaporator 120 b has the same configurationas the evaporator 120 a.

As shown in FIG. 12, a flowmeter 181 and a thermometer 182 are installedon an outlet pipe 107 running from the heating tube 103 a. Also, adifferential pressure gage 183 is connected across an inlet pipe 106running to the heating tube 103 a and the outlet pipe 107 running fromthe heating tube 103 a. Such devices are used for detecting whether ornot the temperature of the aqueous solution is different from thedetermined one, whether or not the flow rate of the aqueous solution isdifferent from the determined one. Otherwise, the devices are used fordetecting whether or not the differential pressure of aqueous solutionbetween the inlet and the outlet is different from the determined one.The device enables the heating tube 3 a to be detected whether or notthe hydrate blocking procedure has begun. Means for cancelingsupercooling 200 is, also, provided on the outlet pipe 107 on thedownstream side of such devices.

When the flow-meter 181, the thermometer 182, or the differentialpressure gage 183 indicates that the heating tube 103 a has entered intothe blocking stage, the detection signal is sent to thesolenoid-operated valves as described above. Such an input signal intothe solenoid-operated valves enables the evaporator 120 a to enter intothe melting operation.

Furthermore, the signal of the flowmeter 181, the thermometer 182, orthe differential pressure gage 183 can be used for controlling therefrigerating performance of the refrigerating machine so as tosupercool the aqueous solution of the guest compound.

The means for canceling supercooling shown in FIG. 13 has an injectionport 207 for injecting hydrate from hydrate slurry vessel 205 into theoutlet pipe 107 via a pump 206. When the supercooled aqueous solutiongets into contact with the hydrate injected through the injection port207, the injected hydrate makes it possible easily to generate thehydrate, simultaneously with the generated hydrate as nucleus.

As shown in FIG. 14, the configuration may be a case such that a bypasspipe 220 is located onto the outlet pipe 107, flow path switching valves221 and 222 are located onto the outlet pipe 107 and the bypass pipe230, respectively. And the means for canceling supercooling such as acooling portion 202 of a small refrigerating machine is located in thebypass pipe 230.

With reference to FIGS. 15 and 16, the apparatus for generating thehydrate slurry are described in accordance with other examples of theexemplary embodiment. The apparatus for generating the hydrate slurryuses a compression-refrigerating machine, which has two switchableevaporators. First, the configuration, which is common to FIG. 15 andFIG. 16, is explained. And then the different configuration between FIG.15 and FIG. 16 is explained.

In FIGS. 15 and 16, the essential components of the compressionrefrigerating machine are two evaporators 301 a and 301 b, which arealso used as heat exchangers for generating hydrate slurry, a compressor302, a condenser 303, and expansion valves 304 a and 304 b correspondingthe evaporators. The evaporators 301 a and 301 b shown in FIGS. 15 and16 are shell-and-tube type heat exchangers or plate type heatexchangers, where exchanging the heat is done via a heat transfersurface. In of case the shell-and-tube type heat generator, the aqueoussolution of the guest compound flows on the tube (heating tube) side.And a refrigerant flows on the shell side. The aqueous solution of theguest compound circulates in a circulation system, where the aqueoussolution of the guest compound, is transported from a thermal storagetank (not shown) to the heating tube located in the evaporator via anaqueous solution pump 305. And the aqueous solution is supercooled. Andthen, canceling supercooling to form hydrate slurry, the aqueoussolution returns back into the thermal storage tank. Although not shownin the above-mentioned Figs., detecting means, means for cancelingsupercooling, and the like are also provided as the same as FIG. 11.

The apparatus for generating the hydrate slurry shown in FIG. 15performs the operation, using the evaporator 301 a. That is, theapparatus cools the aqueous solution of the guest compound that flows ina heating tube located in the evaporator 301 a. At this stage, asolenoid-operated valve 313 and solenoid-operated valves 311 a and 312 aon the upstream and downstream sides of the evaporator 301 a opens, andsolenoid-operated valves 311 b and 312 b on the upstream and downstreamsides of the evaporator 301 b are closed.

When the heating tube in the evaporator 301 a enters into the blockingprocedure, the solenoid-operated valves 311 a and 312 a on the upstreamand downstream sides of the evaporator 301 a are closed, and thesolenoid-operated valves 311 b and 312 b on the upstream and downstreamsides of the evaporator 301 b open. Using the evaporator 301 b makes itpossible to continue to operate generating the hydrate slurry. On theother hand, keeping solenoid-operated valves 314 a and 315 a open, ahigh-temperature and high-pressure refrigerant liquid at the outlet ofthe condenser 303 flows into the evaporator 301 a, by way of bypassing.In such a way, melting operation is done (the condensed refrigerantliquid passes by way of the bypass line). The refrigerant liquid, whosetemperature has decreased by the melting operation, is sent to the otherevaporator 301 b. There may be a contrary case that the heating tube inthe evaporator 301 b enters into the blocking procedure. In this case,the same operation is the same as described above.

In FIG. 16, there may be a case that for generating the hydrate slurryperforms the operation using the evaporator 301 a. That is, theapparatus cools the aqueous solution of the guest compound. In theprocedure, the aqueous solution flows in the heating tube located in theevaporator 301 a. When the heating tube in the evaporator 301 a entersinto the blocking procedure, the solenoid-operated valve 311 a isclosed, and a solenoid-operated valve 316 a opens. Thus, ahigh-temperature and high-pressure refrigerant gas at the outlet of thecompressor 302 flows by way of the bypassing line. And then meltingoperation is performed (the condensed refrigerant gas passes by way ofthe bypass line).

Although not shown in FIG. 16, for the evaporator 301 b as well, abypass pipe and a solenoid-operated valve corresponding to the bypasspipe and the solenoid-operated valve 316 a for the evaporator 301 a areprovided. When the heating tube in the evaporator 301 b enters into theblocking procedure, the same operation as described above is performed.

The apparatus for generating the hydrate slurry shown in FIG. 15 andFIG. 16 also achieve the same effects as those of the system shown inFIG. 11.

As described above in detail, according to the present invention, theapparatus for generating the hydrate slurry makes it possible to obtainthe cost reduction and energy saving, resulting from deleting a platetype or a multitubular type heat exchanger and a pump.

1. An apparatus for generating a hydrate slurry, wherein the hydrateslurry is a mixture of an aqueous solution containing a guest compoundand a hydrate of the guest compound, the hydrate being generated bycooling the aqueous solution at a temperature of more than 0° C., theapparatus comprising a first heat exchanger, at least one second heatexchanger and a canceling device, the first heat exchanger beingconfigured for supercooling the aqueous solution to generate asupercooled aqueous solution, while holding the aqueous solution in aliquid state, the canceling device being provided on the downstream sideof the first heat exchanger, the canceling device being configured tocancel the supercooling of the aqueous solution, and the at least onesecond heat exchanger being provided on the downstream side of the firstheat exchanger, the at least one second heat exchanger being configuredto cool the hydrate slurry generated from the aqueous solution, thesupercooling of which is canceled by the canceling device.
 2. Theapparatus according to claim 1, wherein the at least one second heatexchanger comprises a plurality of second heat exchangers which areswitchable.
 3. The apparatus according to claim 2, wherein when adhesionof the hydrate is detected in a second heat exchanger of the pluralityof the second heat exchangers in which the hydrate slurry is generated,the generation of the hydrate slurry is stopped in said second heatexchanger, the adhered hydrate is melted therein, and the hydrate slurryis generated in another second heat exchanger of the plurality of thesecond heat exchangers.
 4. The apparatus according to claim 2, whereinthe plurality of the second heat exchangers are switched oversuccessively at a fixed time interval within which hydrate which becomesadhered is melted.
 5. The apparatus according to claim 1, wherein thecanceling device comprises a device for introducing the hydrate slurryinto the supercooled aqueous solution supercooled by the first heatexchanger.
 6. The apparatus according to claim 5, wherein thesupercooled aqueous solution has a supercooling degree of 0.7° C. ormore.
 7. The apparatus according to claim 5, wherein the hydrate slurryintroduced into the supercooled aqueous solution is in an amount of 1vol % or more of the total amount of the supercooled aqueous solution.8. The apparatus according to claim 5, wherein the hydrate slurryintroduced into the supercooled aqueous solution is in an amount of 1.8vol % or more of the total amount of the supercooled aqueous solution.9. The apparatus according to claim 5, wherein the supercooled aqueoussolution has a Reynolds number of 4500 or more.
 10. The apparatusaccording to claim 5, wherein the hydrate slurry introduced into thesupercooled aqueous solution is generated by the at least one, secondheat exchanger.
 11. The apparatus according to claim 5, wherein thehydrate slurry introduced into the supercooled aqueous solution isaccommodated in a thermal storage tank for the hydrate slurry.
 12. Theapparatus according to claim 1, wherein the canceling device is selectedfrom the group consisting of a cooling portion of a small refrigeratingmachine, a low-temperature protrusion, an oscillating portion of anultrasonic oscillator, a low-frequency oscillator, a static mixer, amixing blade and a pump.
 13. The apparatus according to claim 1, whereinthe guest compound is at least one compound selected from the groupconsisting of tetra-n-butyl ammonium salt, tetra-iso-amyl ammonium salt,tetra-n-butyl phosphonium salt and tetra-iso-amyl sulfonium salt.
 14. Inan apparatus for generating a hydrate slurry containing a hydrate of aguest compound produced by cooling an aqueous solution containing theguest compound at a temperature of higher than 0° C., the apparatuscomprising: a refrigerator configured to cool a refrigerant and providea cooled refrigerant, the refrigerator having a plurality ofevaporators, the plurality of evaporators being provided so as to beswitchable and the cooled refrigerant flowing in one or more of theplurality of evaporators; a circulation system configured to cool theaqueous solution of the guest compound by the cooled refrigerant in oneor more of the plurality of the evaporators; a controller configured to(i) stop the cooling of the aqueous solution of the guest compound inone evaporator of the plurality of the evaporators, when a blockage ofthe circulation system occurs due to a hydrate which is generated by thecooling thereof, and (ii) start the cooling of the aqueous solution ofthe guest compound in another evaporator of the plurality ofevaporators; and a device for supplying the refrigerant at a hightemperature from the refrigerator to the evaporator in which the coolingof the aqueous solution of the guest compound is stopped so as to meltthe hydrate causing the blockage of the circulation system.
 15. Theapparatus according to claim 14, further comprising a detectorconfigured to detect the blockage of the circulation system.
 16. Theapparatus according to claim 15, wherein the detector is at least onedetector selected from the group consisting of (i) a flowmeter providedon an outlet pipe of one evaporator of the plurality of evaporators,(ii) a thermometer provided on an outlet pipe of one evaporator of theplurality of evaporators and (iii) a differential pressure gaugeprovided across an inlet pipe and an outlet pipe of the one evaporatorof the plurality of evaporators.
 17. The apparatus according to claim14, wherein the refrigerator is an absorption refrigerating machinehaving an absorber and has a device for supplying the refrigerant in agaseous state generated by the generator to the evaporator of theplurality of evaporators in which the cooling of the aqueous solution ofthe guest compound is stopped.
 18. The apparatus according to claim 14,wherein the refrigerator is a compression refrigerating machine having acompressor and a device for supplying the refrigerant in a gaseous stategenerated by the compressor to the evaporator of the plurality ofevaporators in which the cooling of the aqueous solution of the guestcompound is stopped.
 19. The apparatus according to claim 14, whereinthe refrigerator is a compression refrigerating machine having acondenser and a device for supplying the refrigerant in a liquid stategenerated by the condenser to the evaporator of the plurality ofevaporators in which the cooling of the aqueous solution of the guestcompound is stopped.
 20. The apparatus according to any one of claims 14to 19, wherein the aqueous solution of the guest compound is supercooledby one or more of the plurality of the evaporators; and a cancelingdevice is located on an outlet pipe of said one or more of the pluralityof evaporators so as to cancel the supercooling of the aqueous solution.21. The apparatus according to claim 20, wherein the canceling device isselected from the group consisting of a cooling portion of a smallrefrigerating machine, a low-temperature protrusion, an oscillatingportion of an ultrasonic oscillator, a low-frequency oscillator, hydrateslurry injecting means, a static mixer, a mixing blade and a pump. 22.The apparatus according to any one of claims 14 to 19, wherein the guestcompound is at least one compound selected from the group consisting oftetra-n-butyl ammonium salt, tetra-iso-amyl ammonium salt,tetra-iso-butyl phosphonium salt and tri-iso-amyl sulfonium salt.